Storage system architecture

ABSTRACT

A storage system is provided. The storage system includes a plurality of storage units, each of the plurality of storage units having storage memory for user data and a plurality of storage nodes, each of the plurality of storage nodes configured to have ownership of a portion of the user data. The storage system includes a first pathway, coupling the plurality of storage units such that each of the plurality of storage units can communicate with at least one other of the plurality of storage units via the first pathway without assistance from the plurality of storage nodes.

BACKGROUND

Solid-state memory, such as flash, is currently in use in solid-statedrives (SSD) to augment or replace conventional hard disk drives (HDD),writable CD (compact disk) or writable DVD (digital versatile disk)drives, collectively known as spinning media, and tape drives, forstorage of large amounts of data. Flash and other solid-state memorieshave characteristics that differ from spinning media. Yet, manysolid-state drives are designed to conform to hard disk drive standardsfor compatibility reasons, which makes it difficult to provide enhancedfeatures or take advantage of unique aspects of flash and othersolid-state memory. Spinning media are limited in the flexibility orvariations of the connections communication paths between the storageunits or storage nodes of conventional storage arrays.

It is within this context that the embodiments arise.

SUMMARY

In some embodiments, a storage system is provided. The storage systemincludes a plurality of storage units, each of the plurality of storageunits having storage memory for user data and a plurality of storagenodes, each of the plurality of storage nodes configured to haveownership of a portion of the user data. The storage system includes afirst pathway, coupling the plurality of storage units such that each ofthe plurality of storage units can communicate with at least one otherof the plurality of storage units via the first pathway withoutassistance from the plurality of storage nodes.

In some embodiments, a storage cluster is provided. The storage clusterincludes a single chassis, having a plurality of slots, each slotconfigured to receive a storage node or a storage unit, each of whichcan occupy one or more of the plurality of slots. The storage clusterincludes a plurality of storage units in the single chassis, each of theplurality of storage units having solid-state storage memory for userdata. The storage cluster includes a first pathway, in the singlechassis and coupling the plurality of storage units such that no storagenode intervenes in or assists communication via the first pathway from afirst one of the plurality of storage units to a second one of theplurality of storage units.

In some embodiments, a storage system in a single chassis is provided.The storage system includes a plurality of storage units in the singlechassis, each of the plurality of storage units having solid-statestorage memory for user data. The storage system includes a firstpathway in the single chassis, each of the plurality of storage unitscoupled to communicate with at least one other of the plurality ofstorage units via the first pathway. The storage system includes aplurality of storage nodes in the single chassis, each of the pluralityof storage nodes having a subset of the plurality of storage unitstherein and having ownership of a portion of the user data, wherein theplurality of storage nodes are non-participatory in direct communicationbetween storage units. The storage system includes a second pathway inthe single chassis, coupling the plurality of storage nodes.

Other aspects and advantages of the embodiments will become apparentfrom the following detailed description taken in conjunction with theaccompanying drawings which illustrate, by way of example, theprinciples of the described embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The described embodiments and the advantages thereof may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings. These drawings in no waylimit any changes in form and detail that may be made to the describedembodiments by one skilled in the art without departing from the spiritand scope of the described embodiments.

FIG. 1 is a perspective view of a storage cluster with multiple storagenodes and internal storage coupled to each storage node to providenetwork attached storage, in accordance with some embodiments.

FIG. 2 is a system diagram of an enterprise computing system, which canuse one or more of the storage clusters of FIG. 1 as a storage resourcein some embodiments.

FIG. 3 is a block diagram showing multiple storage nodes andnon-volatile solid state storage with differing capacities, suitable foruse in the storage cluster of FIG. 1 in accordance with someembodiments.

FIG. 4 is a block diagram showing an interconnect switch couplingmultiple storage nodes in accordance with some embodiments.

FIG. 5 is a multiple level block diagram, showing contents of a storagenode and contents of one of the non-volatile solid state storage unitsin accordance with some embodiments.

FIG. 6A is a block diagram of a further embodiment of the storagecluster having one example of connectivity between and within storagenodes and storage units in accordance with some embodiments.

FIG. 6B is a variation of the connectivity within the storage cluster ofFIG. 6A in accordance with some embodiments.

FIG. 7 is a block diagram of a further embodiment of the storage clusterof FIGS. 1-5, suitable for data storage or a combination of data storageand computing in accordance with some embodiments.

FIG. 8A is a block diagram of a further embodiment of connectivitywithin the storage cluster of FIGS. 1-5, with switches in accordancewith some embodiments.

FIG. 8B is a variation of connectivity within the storage cluster ofFIG. 8A, with the switches coupling the storage units in accordance withsome embodiments.

FIG. 9A is a block diagram of one example of an architecture for computenodes coupled together for the storage cluster in accordance with someembodiments.

FIG. 9B is a block diagram of a further embodiment of the storagecluster of FIGS. 1-5, with the compute nodes of FIG. 9A in accordancewith some embodiments.

FIG. 9C is a block diagram of a variation of the storage cluster withcompute nodes of FIG. 9B, depicting storage nodes, storage units andcompute nodes in multiple chassis, all coupled together as one or morestorage clusters and variations of connectivity within a chassis andbetween chassis in accordance with some embodiments.

FIG. 10 is a flow diagram of a method for operating a storage cluster,which can be practiced on or by embodiments of the storage cluster,storage nodes and/or non-volatile solid state storages or storage unitsin accordance with some embodiments.

FIG. 11 is an illustration showing an exemplary computing device whichmay implement the embodiments described herein.

DETAILED DESCRIPTION

The embodiments below describe a storage cluster that stores user data,such as user data originating from one or more user or client systems orother sources external to the storage cluster. The storage clusterdistributes user data across storage nodes housed within a chassis,using erasure coding and redundant copies of metadata. Erasure codingrefers to a method of data protection or reconstruction in which data isstored across a set of different locations, such as disks, storage nodesor geographic locations. Flash memory is one type of solid-state memorythat may be integrated with the embodiments, although the embodimentsmay be extended to other types of solid-state memory or other storagemedium, including non-solid state memory. Control of storage locationsand workloads are distributed across the storage locations in aclustered peer-to-peer system. Tasks such as mediating communicationsbetween the various storage nodes, detecting when a storage node hasbecome unavailable, and balancing I/Os (inputs and outputs) across thevarious storage nodes, are all handled on a distributed basis. Data islaid out or distributed across multiple storage nodes in data fragmentsor stripes that support data recovery in some embodiments. Ownership ofdata can be reassigned within a cluster, independent of input and outputpatterns. This architecture described in more detail below allows astorage node in the cluster to fail, with the system remainingoperational, since the data can be reconstructed from other storagenodes and thus remain available for input and output operations. Invarious embodiments, a storage node may be referred to as a clusternode, a blade, or a server.

The storage cluster is contained within a chassis, i.e., an enclosurehousing one or more storage nodes. A mechanism to provide power to eachstorage node, such as a power distribution bus, and a communicationmechanism, such as a communication bus that enables communicationbetween the storage nodes are included within the chassis. The storagecluster can run as an independent system in one location according tosome embodiments. In one embodiment, a chassis contains at least twoinstances of both the power distribution and the communication bus whichmay be enabled or disabled independently. The internal communication busmay be an Ethernet bus, however, other technologies such as PeripheralComponent Interconnect (PCI) Express, InfiniBand, and others, areequally suitable. The chassis provides a port for an externalcommunication bus for enabling communication between multiple chassis,directly or through a switch, and with client systems. The externalcommunication may use a technology such as Ethernet, InfiniBand, FibreChannel, etc. In some embodiments, the external communication bus usesdifferent communication bus technologies for inter-chassis and clientcommunication. If a switch is deployed within or between chassis, theswitch may act as a translation between multiple protocols ortechnologies. When multiple chassis are connected to define a storagecluster, the storage cluster may be accessed by a client using eitherproprietary interfaces or standard interfaces such as network filesystem (NFS), common internet file system (CIFS), small computer systeminterface (SCSI) or hypertext transfer protocol (HTTP). Translation fromthe client protocol may occur at the switch, chassis externalcommunication bus or within each storage node.

Each storage node may be one or more storage servers and each storageserver is connected to one or more non-volatile solid state memoryunits, which may be referred to as storage units. One embodimentincludes a single storage server in each storage node and between one toeight non-volatile solid state memory units, however this one example isnot meant to be limiting. The storage server may include a processor,dynamic random access memory (DRAM) and interfaces for the internalcommunication bus and power distribution for each of the power buses.Inside the storage node, the interfaces and storage unit share acommunication bus, e.g., PCI Express, in some embodiments. Thenon-volatile solid state memory units may directly access the internalcommunication bus interface through a storage node communication bus, orrequest the storage node to access the bus interface. The non-volatilesolid state memory unit contains an embedded central processing unit(CPU), solid state storage controller, and a quantity of solid statemass storage, e.g., between 2-32 terabytes (TB) in some embodiments. Anembedded volatile storage medium, such as DRAM, and an energy reserveapparatus are included in the non-volatile solid state memory unit. Insome embodiments, the energy reserve apparatus is a capacitor,super-capacitor, or battery that enables transferring a subset of DRAMcontents to a stable storage medium in the case of power loss. In someembodiments, the non-volatile solid state memory unit is constructedwith a storage class memory, such as phase change or magnetoresistiverandom access memory (MRAM) that substitutes for DRAM and enables areduced power hold-up apparatus.

One of many features of the storage nodes and non-volatile solid statestorage is the ability to proactively rebuild data in a storage cluster.The storage nodes and non-volatile solid state storage can determinewhen a storage node or non-volatile solid state storage in the storagecluster is unreachable, independent of whether there is an attempt toread data involving that storage node or non-volatile solid statestorage. The storage nodes and non-volatile solid state storage thencooperate to recover and rebuild the data in at least partially newlocations. This constitutes a proactive rebuild, in that the systemrebuilds data without waiting until the data is needed for a read accessinitiated from a client system employing the storage cluster. These andfurther details of the storage memory and operation thereof arediscussed below.

FIG. 1 is a perspective view of a storage cluster 160, with multiplestorage nodes 150 and internal solid-state memory coupled to eachstorage node to provide network attached storage or storage areanetwork, in accordance with some embodiments. A network attachedstorage, storage area network, or a storage cluster, or other storagememory, could include one or more storage clusters 160, each having oneor more storage nodes 150, in a flexible and reconfigurable arrangementof both the physical components and the amount of storage memoryprovided thereby. The storage cluster 160 is designed to fit in a rack,and one or more racks can be set up and populated as desired for thestorage memory. The storage cluster 160 has a chassis 138 havingmultiple slots 142. It should be appreciated that chassis 138 may bereferred to as a housing, enclosure, or rack unit. In one embodiment,the chassis 138 has fourteen slots 142, although other numbers of slotsare readily devised. For example, some embodiments have four slots,eight slots, sixteen slots, thirty-two slots, or other suitable numberof slots. Each slot 142 can accommodate one storage node 150 in someembodiments. Chassis 138 includes flaps 148 that can be utilized tomount the chassis 138 on a rack. Fans 144 provide air circulation forcooling of the storage nodes 150 and components thereof, although othercooling components could be used, or an embodiment could be devisedwithout cooling components. A switch fabric 146 couples storage nodes150 within chassis 138 together and to a network for communication tothe memory. In an embodiment depicted in FIG. 1, the slots 142 to theleft of the switch fabric 146 and fans 144 are shown occupied by storagenodes 150, while the slots 142 to the right of the switch fabric 146 andfans 144 are empty and available for insertion of storage node 150 forillustrative purposes. This configuration is one example, and one ormore storage nodes 150 could occupy the slots 142 in various furtherarrangements. The storage node arrangements need not be sequential oradjacent in some embodiments. Storage nodes 150 are hot pluggable,meaning that a storage node 150 can be inserted into a slot 142 in thechassis 138, or removed from a slot 142, without stopping or poweringdown the system. Upon insertion or removal of storage node 150 from slot142, the system automatically reconfigures in order to recognize andadapt to the change. Reconfiguration, in some embodiments, includesrestoring redundancy and/or rebalancing data or load.

Each storage node 150 can have multiple components. In the embodimentshown here, the storage node 150 includes a printed circuit board 158populated by a CPU 156, i.e., processor, a memory 154 coupled to the CPU156, and a non-volatile solid state storage 152 coupled to the CPU 156,although other mountings and/or components could be used in furtherembodiments. The memory 154 has instructions which are executed by theCPU 156 and/or data operated on by the CPU 156. As further explainedbelow, the non-volatile solid state storage 152 includes flash or, infurther embodiments, other types of solid-state memory.

FIG. 2 is a system diagram of an enterprise computing system 102, whichcan use one or more of the storage nodes, storage clusters and/ornon-volatile solid state storage of FIG. 1 as a storage resource 108.For example, flash storage 128 of FIG. 2 may integrate the storagenodes, storage clusters and/or non-volatile solid state storage of FIG.1 in some embodiments. The enterprise computing system 102 hasprocessing resources 104, networking resources 106 and storage resources108, including flash storage 128. A flash controller 130 and flashmemory 132 are included in the flash storage 128. In variousembodiments, the flash storage 128 could include one or more storagenodes or storage clusters, with the flash controller 130 including theCPUs, and the flash memory 132 including the non-volatile solid statestorage of the storage nodes. In some embodiments flash memory 132 mayinclude different types of flash memory or the same type of flashmemory. The enterprise computing system 102 illustrates an environmentsuitable for deployment of the flash storage 128, although the flashstorage 128 could be used in other computing systems or devices, largeror smaller, or in variations of the enterprise computing system 102,with fewer or additional resources. The enterprise computing system 102can be coupled to a network 140, such as the Internet, in order toprovide or make use of services. For example, the enterprise computingsystem 102 could provide cloud services, physical computing resources,or virtual computing services.

In the enterprise computing system 102, various resources are arrangedand managed by various controllers. A processing controller 110 managesthe processing resources 104, which include processors 116 andrandom-access memory (RAM) 118. Networking controller 112 manages thenetworking resources 106, which include routers 120, switches 122, andservers 124. A storage controller 114 manages storage resources 108,which include hard drives 126 and flash storage 128. Other types ofprocessing resources, networking resources, and storage resources couldbe included with the embodiments. In some embodiments, the flash storage128 completely replaces the hard drives 126. The enterprise computingsystem 102 can provide or allocate the various resources as physicalcomputing resources, or in variations, as virtual computing resourcessupported by physical computing resources. For example, the variousresources could be implemented using one or more servers executingsoftware. Files or data objects, or other forms of data, are stored inthe storage resources 108.

In various embodiments, an enterprise computing system 102 could includemultiple racks populated by storage clusters, and these could be locatedin a single physical location such as in a cluster or a server farm. Inother embodiments the multiple racks could be located at multiplephysical locations such as in various cities, states or countries,connected by a network. Each of the racks, each of the storage clusters,each of the storage nodes, and each of the non-volatile solid statestorage could be individually configured with a respective amount ofstorage space, which is then reconfigurable independently of the others.Storage capacity can thus be flexibly added, upgraded, subtracted,recovered and/or reconfigured at each of the non-volatile solid statestorages. As mentioned previously, each storage node could implement oneor more servers in some embodiments.

FIG. 3 is a block diagram showing multiple storage nodes 150 andnon-volatile solid state storage 152 with differing capacities, suitablefor use in the chassis of FIG. 1. Each storage node 150 can have one ormore units of non-volatile solid state storage 152. Each non-volatilesolid state storage 152 may include differing capacity from othernon-volatile solid state storage 152 on a storage node 150 or in otherstorage nodes 150 in some embodiments. Alternatively, all of thenon-volatile solid state storages 152 on a storage node or on multiplestorage nodes can have the same capacity or combinations of the sameand/or differing capacities. This flexibility is illustrated in FIG. 3,which shows an example of one storage node 150 having mixed non-volatilesolid state storage 152 of four, eight and thirty-two TB capacity,another storage node 150 having non-volatile solid state storage 152each of thirty-two TB capacity, and still another storage node havingnon-volatile solid state storage 152 each of eight TB capacity. Variousfurther combinations and capacities are readily devised in accordancewith the teachings herein. In the context of clustering, e.g.,clustering storage to form a storage cluster, a storage node can be orinclude a non-volatile solid state storage 152. Non-volatile solid statestorage 152 is a convenient clustering point as the non-volatile solidstate storage 152 may include a nonvolatile random access memory (NVRAM)component, as will be further described below.

Referring to FIGS. 1 and 3, storage cluster 160 is scalable, meaningthat storage capacity with non-uniform storage sizes is readily added,as described above. One or more storage nodes 150 can be plugged into orremoved from each chassis and the storage cluster self-configures insome embodiments. Plug-in storage nodes 150, whether installed in achassis as delivered or later added, can have different sizes. Forexample, in one embodiment a storage node 150 can have any multiple of 4TB, e.g., 8 TB, 12 TB, 16 TB, 32 TB, etc. In further embodiments, astorage node 150 could have any multiple of other storage amounts orcapacities. Storage capacity of each storage node 150 is broadcast, andinfluences decisions of how to stripe the data. For maximum storageefficiency, an embodiment can self-configure as wide as possible in thestripe, subject to a predetermined requirement of continued operationwith loss of up to one, or up to two, non-volatile solid state storageunits 152 or storage nodes 150 within the chassis.

FIG. 4 is a block diagram showing a communications interconnect 170 andpower distribution bus 172 coupling multiple storage nodes 150.Referring back to FIG. 1, the communications interconnect 170 can beincluded in or implemented with the switch fabric 146 in someembodiments. Where multiple storage clusters 160 occupy a rack, thecommunications interconnect 170 can be included in or implemented with atop of rack switch, in some embodiments. As illustrated in FIG. 4,storage cluster 160 is enclosed within a single chassis 138. Externalport 176 is coupled to storage nodes 150 through communicationsinterconnect 170, while external port 174 is coupled directly to astorage node. External power port 178 is coupled to power distributionbus 172. Storage nodes 150 may include varying amounts and differingcapacities of non-volatile solid state storage 152 as described withreference to FIG. 3. In addition, one or more storage nodes 150 may be acompute only storage node as illustrated in FIG. 4. A compute onlystorage node 150 performs computing functions for the storage cluster160, or functions as a compute node to perform computing functionsand/or execute applications, which may make use of user data destinedfor, stored in, or retrieved from the non-volatile solid state storages152 in the storage cluster 160, in various embodiments. Authorities 168are implemented on the non-volatile solid state storages 152, forexample as lists or other data structures stored in memory. In someembodiments the authorities are stored within the non-volatile solidstate storage 152 and supported by software executing on a controller orother processor of the non-volatile solid state storage 152. In afurther embodiment, authorities 168 are implemented on the storage nodes150, for example as lists or other data structures stored in the memory154 and supported by software executing on the CPU 156 of the storagenode 150. Authorities 168 control how and where data is stored in thenon-volatile solid state storages 152 in some embodiments. This controlassists in determining which type of erasure coding scheme is applied tothe data, and which storage nodes 150 have which portions of the data.Each authority 168 may be assigned to a non-volatile solid state storage152. Each authority may control a range of Mode numbers, segmentnumbers, or other data identifiers which are assigned to data by a filesystem, by the storage nodes 150, or by the non-volatile solid statestorage 152, in various embodiments.

Every piece of data, and every piece of metadata, has redundancy in thesystem in some embodiments. In addition, every piece of data and everypiece of metadata has an owner, which may be referred to as anauthority, or in some versions a ward, with an authority being a groupor set of wards. If that authority is unreachable, for example throughfailure of a storage node, there is a plan of succession for how to findthat data or that metadata. In various embodiments, there are redundantcopies of authorities 168. Authorities 168 have a relationship tostorage nodes 150 and non-volatile solid state storage 152 in someembodiments. Each authority 168 (and thus each group of wards, inembodiments where an authority is a group of wards), covering a range ofdata segment numbers or other identifiers of the data, may be assignedto a specific non-volatile solid state storage 152. In some embodimentsthe authorities 168 for all of such ranges are distributed over thenon-volatile solid state storages 152 of a storage cluster. Each storagenode 150 has a network port that provides access to the non-volatilesolid state storage(s) 152 of that storage node 150. Data can be storedin a segment, which is associated with a segment number and that segmentnumber is an indirection for a configuration of a RAID (redundant arrayof independent disks) stripe in some embodiments. The assignment and useof the authorities 168 (and wards, where applicable) thus establishes anindirection to data. Indirection may be referred to as the ability toreference data indirectly, in this case via an authority 168, inaccordance with some embodiments. A segment identifies a set ofnon-volatile solid state storage 152 and a local identifier into the setof non-volatile solid state storage 152 that may contain data. In someembodiments, the local identifier is an offset into the device and maybe reused sequentially by multiple segments. In other embodiments thelocal identifier is unique for a specific segment and never reused. Theoffsets in the non-volatile solid state storage 152 are applied tolocating data for writing to or reading from the non-volatile solidstate storage 152 (in the form of a RAID stripe). Data is striped acrossmultiple units of non-volatile solid state storage 152, which mayinclude or be different from the non-volatile solid state storage 152having the authority 168 for a particular data segment.

If there is a change in where a particular segment of data is located,e.g., during a data move or a data reconstruction, the authority 168 forthat data segment should be consulted, at that non-volatile solid statestorage 152 or storage node 150 having that authority 168. In order tolocate a particular piece of data, embodiments calculate a hash valuefor a data segment or apply an Mode number or a data segment number. Theoutput of this operation points to a non-volatile solid state storage152 having the authority 168 for that particular piece of data. In someembodiments there are two stages to this operation. The first stage mapsan entity identifier (ID), e.g., a segment number, Mode number, ordirectory number to an authority identifier. This mapping may include acalculation such as a hash or a bit mask. The second stage is mappingthe authority identifier to a particular non-volatile solid statestorage 152, which may be done through an explicit mapping. Theoperation is repeatable, so that when the calculation is performed, theresult of the calculation repeatably and reliably points to a particularnon-volatile solid state storage 152 having that authority 168. Theoperation may include the set of reachable storage nodes as input. Ifthe set of reachable non-volatile solid state storage units changes theoptimal set changes. In some embodiments, the persisted value is thecurrent assignment (which is always true) and the calculated value isthe target assignment the cluster will attempt to reconfigure towards.This calculation may be used to determine the optimal non-volatile solidstate storage 152 for an authority in the presence of a set ofnon-volatile solid state storage 152 that are reachable and constitutethe same cluster. The calculation also determines an ordered set of peernon-volatile solid state storage 152 that will also record the authorityto non-volatile solid state storage mapping so that the authority may bedetermined even if the assigned non-volatile solid state storage isunreachable. A duplicate or substitute authority 168 may be consulted ifa specific authority 168 is unavailable in some embodiments.

With reference to FIGS. 1-4, two of the many tasks of the CPU 156 on astorage node 150 are to break up write data, and reassemble read data.When the system has determined that data is to be written, the authority168 for that data is located as above. When the segment ID for data isalready determined the request to write is forwarded to the non-volatilesolid state storage 152 currently determined to be the host of theauthority 168 determined from the segment. The host CPU 156 of thestorage node 150, on which the non-volatile solid state storage 152 andcorresponding authority 168 reside, then breaks up or shards the dataand transmits the data out to various non-volatile solid state storage152. The transmitted data is written as a data stripe in accordance withan erasure coding scheme. In some embodiments, data is requested to bepulled, and in other embodiments, data is pushed. In reverse, when datais read, the authority 168 for the segment ID containing the data islocated as described above. The host CPU 156 of the storage node 150 onwhich the non-volatile solid state storage 152 and correspondingauthority 168 reside requests the data from the non-volatile solid statestorage and corresponding storage nodes pointed to by the authority. Insome embodiments the data is read from flash storage as a data stripe.The host CPU 156 of storage node 150 then reassembles the read data,correcting any errors (if present) according to the appropriate erasurecoding scheme, and forwards the reassembled data to the network. Infurther embodiments, some or all of these tasks can be handled in thenon-volatile solid state storage 152. In some embodiments, the segmenthost requests the data be sent to storage node 150 by requesting pagesfrom storage and then sending the data to the storage node making theoriginal request.

In some systems, for example in UNIX-style file systems, data is handledwith an index node or Mode, which specifies a data structure thatrepresents an object in a file system. The object could be a file or adirectory, for example. Metadata may accompany the object, as attributessuch as permission data and a creation timestamp, among otherattributes. A segment number could be assigned to all or a portion ofsuch an object in a file system. In other systems, data segments arehandled with a segment number assigned elsewhere. For purposes ofdiscussion, the unit of distribution is an entity, and an entity can bea file, a directory or a segment. That is, entities are units of data ormetadata stored by a storage system. Entities are grouped into setscalled authorities. Each authority has an authority owner, which is astorage node that has the exclusive right to update the entities in theauthority. In other words, a storage node contains the authority, andthat the authority, in turn, contains entities.

A segment is a logical container of data in accordance with someembodiments. A segment is an address space between medium address spaceand physical flash locations, i.e., the data segment number, are in thisaddress space. Segments may also contain metadata, which enable dataredundancy to be restored (rewritten to different flash locations ordevices) without the involvement of higher level software. In oneembodiment, an internal format of a segment contains client data andmedium mappings to determine the position of that data. Each datasegment is protected, e.g., from memory and other failures, by breakingthe segment into a number of data and parity shards, where applicable.The data and parity shards are distributed, i.e., striped, acrossnon-volatile solid state storage 152 coupled to the host CPUs 156 (SeeFIG. 5) in accordance with an erasure coding scheme. Usage of the termsegments refers to the container and its place in the address space ofsegments in some embodiments. Usage of the term stripe refers to thesame set of shards as a segment and includes how the shards aredistributed along with redundancy or parity information in accordancewith some embodiments.

A series of address-space transformations takes place across an entirestorage system. At the top is the directory entries (file names) whichlink to an inode. Inodes point into medium address space, where data islogically stored. Medium addresses may be mapped through a series ofindirect mediums to spread the load of large files, or implement dataservices like deduplication or snapshots. Medium addresses may be mappedthrough a series of indirect mediums to spread the load of large files,or implement data services like deduplication or snapshots. Segmentaddresses are then translated into physical flash locations. Physicalflash locations have an address range bounded by the amount of flash inthe system in accordance with some embodiments. Medium addresses andsegment addresses are logical containers, and in some embodiments use a128 bit or larger identifier so as to be practically infinite, with alikelihood of reuse calculated as longer than the expected life of thesystem. Addresses from logical containers are allocated in ahierarchical fashion in some embodiments. Initially, each non-volatilesolid state storage 152 may be assigned a range of address space. Withinthis assigned range, the non-volatile solid state storage 152 is able toallocate addresses without synchronization with other non-volatile solidstate storage 152.

Data and metadata is stored by a set of underlying storage layouts thatare optimized for varying workload patterns and storage devices. Theselayouts incorporate multiple redundancy schemes, compression formats andindex algorithms Some of these layouts store information aboutauthorities and authority masters, while others store file metadata andfile data. The redundancy schemes include error correction codes thattolerate corrupted bits within a single storage device (such as a NANDflash chip), erasure codes that tolerate the failure of multiple storagenodes, and replication schemes that tolerate data center or regionalfailures. In some embodiments, low density parity check (LDPC) code isused within a single storage unit. Reed-Solomon encoding is used withina storage cluster, and mirroring is used within a storage grid in someembodiments. Metadata may be stored using an ordered log structuredindex (such as a Log Structured Merge Tree), and large data may not bestored in a log structured layout.

In order to maintain consistency across multiple copies of an entity,the storage nodes agree implicitly on two things through calculations:(1) the authority that contains the entity, and (2) the storage nodethat contains the authority. The assignment of entities to authoritiescan be done by pseudorandomly assigning entities to authorities, bysplitting entities into ranges based upon an externally produced key, orby placing a single entity into each authority. Examples of pseudorandomschemes are linear hashing and the Replication Under Scalable Hashing(RUSH) family of hashes, including Controlled Replication Under ScalableHashing (CRUSH). In some embodiments, pseudorandom assignment isutilized only for assigning authorities to nodes because the set ofnodes can change. The set of authorities cannot change so any subjectivefunction may be applied in these embodiments. Some placement schemesautomatically place authorities on storage nodes, while other placementschemes rely on an explicit mapping of authorities to storage nodes. Insome embodiments, a pseudorandom scheme is utilized to map from eachauthority to a set of candidate authority owners. A pseudorandom datadistribution function related to CRUSH may assign authorities to storagenodes and create a list of where the authorities are assigned. Eachstorage node has a copy of the pseudorandom data distribution function,and can arrive at the same calculation for distributing, and laterfinding or locating an authority. Each of the pseudorandom schemesrequires the reachable set of storage nodes as input in some embodimentsin order to conclude the same target nodes. Once an entity has beenplaced in an authority, the entity may be stored on physical devices sothat no expected failure will lead to unexpected data loss. In someembodiments, rebalancing algorithms attempt to store the copies of allentities within an authority in the same layout and on the same set ofmachines.

Examples of expected failures include device failures, stolen machines,datacenter fires, and regional disasters, such as nuclear or geologicalevents. Different failures lead to different levels of acceptable dataloss. In some embodiments, a stolen storage node impacts neither thesecurity nor the reliability of the system, while depending on systemconfiguration, a regional event could lead to no loss of data, a fewseconds or minutes of lost updates, or even complete data loss.

In the embodiments, the placement of data for storage redundancy isindependent of the placement of authorities for data consistency. Insome embodiments, storage nodes that contain authorities do not containany persistent storage. Instead, the storage nodes are connected tonon-volatile solid state storage units that do not contain authorities.The communications interconnect between storage nodes and non-volatilesolid state storage units consists of multiple communicationtechnologies and has non-uniform performance and fault tolerancecharacteristics. In some embodiments, as mentioned above, non-volatilesolid state storage units are connected to storage nodes via PCIexpress, storage nodes are connected together within a single chassisusing Ethernet backplane, and chassis are connected together to form astorage cluster. Storage clusters are connected to clients usingEthernet or fiber channel in some embodiments. If multiple storageclusters are configured into a storage grid, the multiple storageclusters are connected using the Internet or other long-distancenetworking links, such as a “metro scale” link or private link that doesnot traverse the internet.

Authority owners have the exclusive right to modify entities, to migrateentities from one non-volatile solid state storage unit to anothernon-volatile solid state storage unit, and to add and remove copies ofentities. This allows for maintaining the redundancy of the underlyingdata. When an authority owner fails, is going to be decommissioned, oris overloaded, the authority is transferred to a new storage node.Transient failures make it non-trivial to ensure that all non-faultymachines agree upon the new authority location. The ambiguity thatarises due to transient failures can be achieved automatically by aconsensus protocol such as Paxos, hot-warm failover schemes, via manualintervention by a remote system administrator, or by a local hardwareadministrator (such as by physically removing the failed machine fromthe cluster, or pressing a button on the failed machine). In someembodiments, a consensus protocol is used, and failover is automatic. Iftoo many failures or replication events occur in too short a timeperiod, the system goes into a self-preservation mode and haltsreplication and data movement activities until an administratorintervenes in accordance with some embodiments.

As authorities are transferred between storage nodes and authorityowners update entities in their authorities, the system transfersmessages between the storage nodes and non-volatile solid state storageunits. With regard to persistent messages, messages that have differentpurposes are of different types. Depending on the type of the message,the system maintains different ordering and durability guarantees. Asthe persistent messages are being processed, the messages aretemporarily stored in multiple durable and non-durable storage hardwaretechnologies. In some embodiments, messages are stored in RAM, NVRAM andon NAND flash devices, and a variety of protocols are used in order tomake efficient use of each storage medium. Latency-sensitive clientrequests may be persisted in replicated NVRAM, and then later NAND,while background rebalancing operations are persisted directly to NAND.

Persistent messages are persistently stored prior to being replicated.This allows the system to continue to serve client requests despitefailures and component replacement. Although many hardware componentscontain unique identifiers that are visible to system administrators,manufacturer, hardware supply chain and ongoing monitoring qualitycontrol infrastructure, applications running on top of theinfrastructure address virtualize addresses. These virtualized addressesdo not change over the lifetime of the storage system, regardless ofcomponent failures and replacements. This allows each component of thestorage system to be replaced over time without reconfiguration ordisruptions of client request processing.

In some embodiments, the virtualized addresses are stored withsufficient redundancy. A continuous monitoring system correlateshardware and software status and the hardware identifiers. This allowsdetection and prediction of failures due to faulty components andmanufacturing details. The monitoring system also enables the proactivetransfer of authorities and entities away from impacted devices beforefailure occurs by removing the component from the critical path in someembodiments.

FIG. 5 is a multiple level block diagram, showing contents of a storagenode 150 and contents of a non-volatile solid state storage 152 of thestorage node 150. Data is communicated to and from the storage node 150by a network interface controller (NIC) 202 in some embodiments. Eachstorage node 150 has a CPU 156, and one or more non-volatile solid statestorage 152, as discussed above. Moving down one level in FIG. 5, eachnon-volatile solid state storage 152 has a relatively fast non-volatilesolid state memory, such as nonvolatile random access memory (NVRAM)204, and flash memory 206. In some embodiments, NVRAM 204 may be acomponent that does not require program/erase cycles (DRAM, MRAM, PCM),and can be a memory that can support being written vastly more oftenthan the memory is read from. Moving down another level in FIG. 5, theNVRAM 204 is implemented in one embodiment as high speed volatilememory, such as dynamic random access memory (DRAM) 216, backed up byenergy reserve 218. Energy reserve 218 provides sufficient electricalpower to keep the DRAM 216 powered long enough for contents to betransferred to the flash memory 206 in the event of power failure. Insome embodiments, energy reserve 218 is a capacitor, super-capacitor,battery, or other device, that supplies a suitable supply of energysufficient to enable the transfer of the contents of DRAM 216 to astable storage medium in the case of power loss. The flash memory 206 isimplemented as multiple flash dies 222, which may be referred to aspackages of flash dies 222 or an array of flash dies 222. It should beappreciated that the flash dies 222 could be packaged in any number ofways, with a single die per package, multiple dies per package (i.e.multichip packages), in hybrid packages, as bare dies on a printedcircuit board or other substrate, as encapsulated dies, etc. In theembodiment shown, the non-volatile solid state storage 152 has acontroller 212 or other processor, and an input output (I/O) port 210coupled to the controller 212. I/O port 210 is coupled to the CPU 156and/or the network interface controller 202 of the flash storage node150. Flash input output (I/O) port 220 is coupled to the flash dies 222,and a direct memory access unit (DMA) 214 is coupled to the controller212, the DRAM 216 and the flash dies 222. In the embodiment shown, theI/O port 210, controller 212, DMA unit 214 and flash I/O port 220 areimplemented on a programmable logic device (PLD) 208, e.g., a fieldprogrammable gate array (FPGA). In this embodiment, each flash die 222has pages, organized as sixteen kB (kilobyte) pages 224, and a register226 through which data can be written to or read from the flash die 222.In further embodiments, other types of solid-state memory are used inplace of, or in addition to flash memory illustrated within flash die222.

FIG. 6A is a block diagram of a further embodiment of the storagecluster 160 of FIGS. 1-5. In this embodiment, the components are in achassis 138, such as the chassis 138 with multiple slots shown inFIG. 1. A power supply 606, with a power distribution bus 172 (as seenin FIG. 2), provides electrical power to the various components in thechassis 138. Two storage nodes 150 are shown coupled to a pathway 604,such as a network switch 620 in one embodiment. Further pathways arereadily devised. The pathway 604 couples the storage nodes 150 to eachother, and can also couple the storage nodes 150 to a network externalto the chassis 138, allowing connection to external devices, systems ornetworks.

Multiple storage units 152 are coupled to each other and to the storagenodes 150 by another pathway 602, which is distinct from the networkswitch 620 or other pathway 604 coupling the storage nodes 150. In oneembodiment, the pathway 602 that couples the storage units 152 and thestorage nodes 150 is a PCI Express bus (PCIe), although other busses,networks and various further couplings could be used. In someembodiments, there is transparent bridging for the storage node 150 tocouple to the pathway 602, e.g., to the PCI Express bus.

In order to connect to the two pathways 602, 604, each storage node 150has two ports 608, 610. One of the ports 610 of each storage node 150couples to one of the pathways 604, the other port 608 of each storagenode 150 couples to the other pathway 602.

In some embodiments, each of the storage nodes 150 can perform computefunctions as a compute node. For example, a storage node 150 could runone or more applications. Further, the storage nodes 150 can communicatewith the storage units 152, via the pathway 602, to write and read userdata (e.g., using erasure coding) as described with reference to FIGS.1-3 above. As another example, a storage node 150 executing one or moreapplications could make use of the user data, generating user data forstorage in the storage units 152, reading and processing the user datafrom the storage units 152, etc. Even with loss of one of the storageunits 152, or in some embodiments, loss of two of the storage units 152,the storage nodes 150 and/or remaining storage units 152 can still readthe user data.

In some embodiments, the erasure coding functions are performed mostlyor entirely in the storage units 152, which frees up the computing powerof the storage nodes 150. This allows the storage nodes 150 to focusmore on compute node duties, such as executing one or more applications.In some embodiments, the erasure coding functions are performed mostlyor entirely in the storage nodes 150. This allows the storage nodes 150to focus more on storage node duties. In some embodiments, the erasurecoding functions are shared across the storage nodes 150 and the storageunits 152. This allows the storage nodes 150 to have available computingbandwidth shared between compute node duties and storage node duties.

With the two pathways 602, 604 being distinct from each other, severaladvantages become apparent. Neither pathway 602, 604 becomes abottleneck, as might happen if there were only one pathway coupling thestorage nodes 150 and the storage units 152 to each other and to anexternal network. With only one pathway, a hostile could gain directaccess to the storage units 152 without having to go through a storagenode 150. With two pathways 602, 604, the storage nodes 150 can coupleto each other through one pathway 604, e.g., for multiprocessingapplications or for inter-processor communication. The other pathway 602can be used by either of the storage nodes 150 for data access in thestorage units 152. The architecture shown in FIG. 6A thus supportsvarious storage and computing functions and scenarios. Particularly, oneembodiment as shown in FIG. 6A is a storage and computing system in asingle chassis 138. Processing power, in the form of one or more storagenodes 150, and storage capacity, in the form of one or more storageunits 152, can be added readily to the chassis 138 as storage and/orcomputing needs change.

FIG. 6B is a variation of the storage cluster 160 of FIG. 6A. In thisversion, the pathway 612 has portions specific to storage units 152included in each storage node 150. In one embodiment, the pathway 612 isimplemented as a PCI Express bus coupling together storage units 152 andthe storage node 150. That is, the storage node 150 and storage units152 in one blade share a PCI Express bus in some embodiments. The PCIExpress bus is specific to the blade, and is not coupled directly to thePCI Express bus of another blade. Accordingly, storage units 152 in ablade can communicate with each other and with the storage node 150 inthat blade. Communication from a storage unit 152 or a storage node 150in one blade to a storage node 150 or storage unit 152 in another bladeoccurs via the network switch 620, e.g., the pathway 614.

FIG. 7 is a block diagram of a further embodiment of the storage cluster160 of FIGS. 1-5, suitable for data storage or a combination of datastorage and computing. The version of FIG. 7 has all of the storageunits 152 coupled together by a first pathway 616, which could be a bus,a network or a hardwired mesh, among other possibilities. One storagenode 150 is coupled to each of two storage units 152. Another storageunit 152 is coupled to each of two further storage units 152. Thecoupling from the storage nodes 150 to storage units 152 illustrates asecond pathway 618.

FIG. 8A is a block diagram of a further embodiment of the storagecluster 160 of FIGS. 1-5, with switches 620. One switch 620 couples allof the storage nodes 150 to each other. Another switch 620 also couplesall of the storage nodes 150 together. In this embodiment, each storagenode 150 has two ports, with each port connecting to one of the switches620. This arrangement of ports and switches 620 provides two paths foreach storage node 150 to connect to any other storage node 150. Forexample, the left-most storage node 150 can connect to the rightmoststorage node 150 (or any other storage node 150 in the storage cluster160) via a choice of either the first switch 620 or the second switch620. It should be appreciated that this architecture relievescommunication bottlenecks. Further embodiments with one switch 620, twoswitches 620 coupled to each other, or more than two switches 620, andother numbers of ports, or networks, are readily devised in keeping withthe teachings herein.

FIG. 8B is a variation of the storage cluster 160 of FIG. 8A, with theswitches 620 coupling the storage units 152. As in the embodiment inFIG. 8A, the switches 620 couple the storage nodes 150, providing twopaths for each storage node 150 to communicate with any other storagenode 150. In addition, the switches 620 couple the storage units 152.Two of the storage units 152 in each storage node 150 couple to one ofthe switches 620, and one or more of the storage units 152 in eachstorage node 150 couple to another one of the switches 620. In thismanner, each storage unit 152 can connect to roughly half of the otherstorage units 152 in the storage cluster via one of the switches 620. Ina variation, the switches 620 are coupled to each other (as shown in thedashed line in FIG. 8B), and each storage unit can connect to any otherstorage unit 152 via the switches 620. Further embodiments with oneswitch 620, or other numbers of switches 620 and arrangements ofconnections and the number of components being connected are readilydevised in keeping with the teachings herein.

FIG. 9A is a block diagram of compute nodes 626 coupled together for thestorage cluster 160. A switch 620 couples all of the compute nodes 626together, so that each compute node 626 can communicate with any othercompute node 626 via the switch 620. In various embodiments, eachcompute node 626 could be a compute-only storage node 150 or aspecialized compute node 626. In the embodiment shown, the compute node626 has three processor complexes 628. Each processor complex 628 has aport 630, and may also have local memory and further support (e.g.,digital signal processing, direct memory access, various forms of I/O, agraphics accelerator, one or more processors, and so on). Each port 630is coupled to the switch 620. Thus, each processor complex 628 cancommunicate with each other processor complex 628 via the associatedport 630 and the switch 620, in this architecture. In some embodiments,each processor complex 628 issues a heartbeat (a regular communicationthat can be observed as an indicator of ongoing operation, with the lackof a heartbeat signaling a possible failure or unavailability of thecompute node or processor). In some embodiments, each compute node 626issues a heartbeat. Storage nodes 150 and/or storage units 152 alsoissue heartbeats, in further embodiments.

FIG. 9B is a block diagram of a further embodiment of the storagecluster 160 of FIGS. 1-5, with the compute nodes 626 of FIG. 9A. Thisembodiment is also shown with storage nodes 150. A switch 620 couplesall ports of all of the storage nodes 150, all ports of all of thecompute nodes 626 (e.g., all processor complexes 628 of all of thecompute nodes 626), and all storage units 152. In variations, fewer ormore storage nodes 150, fewer or more compute nodes 626, fewer or morestorage units 152, and fewer or more processor complexes 628 could beinstalled in the chassis 138. Each storage node 150, storage unit 152,or compute node 626 could occupy one or more slots 142 (see FIG. 1) inthe chassis 138. It should be appreciated that FIGS. 9A and 9B are oneexample and not meant to be limiting. In some embodiments multipleswitches 620 may be integrated into chassis 138 and the compute nodes626 may be coupled to the multiple switches in order to achieve thecommunication flexibility provided by the embodiments described herein,similar to the embodiments of FIGS. 8A and 8B.

FIG. 9C is a block diagram of a variation of the storage cluster 160with compute nodes 626 of FIG. 9B, depicting storage nodes 150, storageunits 152 and compute nodes 626 in multiple chassis 138, all coupledtogether as one or more storage clusters 160. Several chassis 138 couldbe rack-mounted and coupled together in the manner depicted, forexpansion of a storage cluster 160. In this embodiment, the switch 620or switches 620 in each chassis 138 couple the components in the chassis138 as described above with reference to FIG. 9B, and the switch 620 orswitches 620 in all of the chassis 138 are coupled together across allof the chassis 138. With various combinations of storage nodes 150and/or compute nodes 626, storage capacity and/or compute capacity(e.g., for running applications, operating system(s), etc.) is readilyconfigured and expanded or contracted, or virtualized in virtualcomputing environments. The use of switches 620 decreases or eliminatesthe usual patch wiring seen in many other rack-mounted systems.

Some embodiments of this and other versions of the storage cluster 160can support two or more independent storage clusters, in one chassis138, two chassis 138, or more chassis 138. Each storage cluster 160 in amulti-storage cluster environment can have storage nodes 150, storageunits 152, and/or compute nodes 626 in one, another, or both or morechassis 138, in various combinations. For example, a first storagecluster 160 could have several storage nodes 150 in one chassis 138 andone or more storage nodes 150 in another chassis 138. A second storagecluster 160 could have one or more storage nodes 150 in the firstchassis 138 and one or more storage nodes 150 in the second chassis 138.Either of these storage clusters 160 could have compute nodes 626 ineither or both of the chassis 138. Each storage cluster 160 could haveits own operating system, and have its own applications executing,independently of the other storage cluster(s) 160.

Multiple features are evident in some or all of the embodiments shown inFIGS. 6A-9C. Many embodiments provide a pathway such that each storageunit 152 can communicate directly with one or more other storage units152 on such a pathway without assistance from any storage node 150. Thatis, a storage unit 152 can communicate with another storage unit 152,via a pathway, with storage nodes 150 being non-participatory in suchcommunication. No storage node 150 intervenes in or assistscommunication via this direct pathway from one storage unit 152 toanother storage unit 152. Some embodiments provide such a direct pathwayfor any communication from any storage unit 152 to any other storageunit 152. Some embodiments provide such a direct pathway forcommunication from each storage unit 152 to one or multiple otherstorage units 152, but not necessarily to all other storage units 152.In these cases, a storage unit 152 could communicate with anotherstorage unit 152 via one or more of the storage nodes 150 and anotherpathway, i.e., with assistance from a storage node 150.

In some embodiments, a pathway for direct communication from one storageunit 152 to any other storage unit 152 is included in couplings of othercomponents of the storage cluster 160. In some embodiments, each storagenode 150 can communicate directly with each storage unit 152 in theentire storage cluster 160. In some embodiments, each storage node 150can communicate with some of the storage units 152 directly, andcommunicate with other storage units 152 via another storage node 150.In some embodiments, the pathways for communication among storage nodes150 and communication among storage units 152 are separated, in othersthese pathways are combined. In some embodiments, the pathways forcommunication between storage nodes 150 and storage units 152, andcommunication among storage units 152 are separated, and in others thesepathways are combined.

One version of the storage node 150 has two ports 608, 610. Both ports608, 610 are employed for communication to other storage nodes 150 via achoice of two different pathways, in some embodiments. One port 610 isemployed for communication to other storage nodes 150 via one pathway,and another port 608 is employed for communication with storage units152 via another pathway, in some embodiments. Both ports 608, 610 areemployed for communication to storage nodes 150 and storage units 152,in some embodiments. By supporting direct communication among storageunits 152, these various architectures can reduce communicationbottlenecks. Storage nodes 150, and the processing and communicationbandwidths are not tied up in supporting the communication among thestorage units 152. As a result of this offloading, storage nodes 150 forfaster operations on user data, or these functions can be transferred tothe storage units 152.

Communications among storage units 152 can include data, metadata,messages to make sure storage units 152 are alive, health and/or statusinformation, etc. With storage units 152 communicating directly withother storage units 152, without a storage node 150 (or processor orcontroller of a storage node 150) intervening, the storage node 150 isfree to manage other processes. Communication between storage nodes 150and storage units 152, or among storage units 152 when these take oversome of the storage node 150 functions, can include data shards, withdata, metadata (e.g., information about and associated with the data)and metametadata (e.g., metadata about the metadata). Such communicationcan also include parity shards, health, status and performanceinformation. By making storage units 152 accessible by other storageunits 152 or by storage nodes 150 (e.g., processors of storage nodes150), the distinction of data ownership can be shifted to varyingdegrees from storage node 150 to storage units 152. This could involveshifting authorities 168 or wards among storage nodes 150 and storageunits 152 in various ways in some embodiments.

With a storage unit 152 on a network, a storage unit 152 couldcommunicate directly with a compute node 626. Such communication couldinvolve embedding a compute node identifier into a request and havingthe storage unit 152 directly return data to the compute node 626instead of returning data to a storage node 150 and then to the computenode 626. Direct connections for data, and data caching could be enabledfor a compute node 626 which has the intelligence to find data instorage units 152. Compute nodes 626 could also be used for specializedprocessing in a data pipeline implementing filtering, transformations,etc., for data going to or coming from storage units 152. Thearchitectures disclosed in FIGS. 6A-9C thus show flexibility forarrangement of components and communication among the components instorage systems and storage and computing systems. Depending upon datathroughput and communication throughput, and absolute or relativeamounts of data and compute function needs and projected growth, onearchitecture may be more suitable than another. Storage capacity andcompute capacity are adjustable, expandable and scalable, in variousembodiments. In addition, the embodiments provide more flexibility forload balancing.

Storage clusters 160, in various embodiments as disclosed herein, can becontrasted with storage arrays in general. The storage nodes 150 arepart of a collection that creates the storage cluster 160. Each storagenode 150 owns a slice of data and computing required to provide thedata. Multiple storage nodes 150 are required to cooperate to store andretrieve the data. Storage memory or storage devices, as used in storagearrays in general, are less involved with processing and manipulatingthe data. Storage memory or storage devices in a storage array receivecommands to read, write, or erase data. The storage memory or storagedevices in a storage array are not aware of a larger system in whichthey are embedded, or what the data means. Storage memory or storagedevices in storage arrays can include various types of storage memory,such as RAM, solid state drives, hard disk drives, etc. The storageunits 152 described herein have multiple interfaces activesimultaneously and serving multiple purposes. In some embodiments, someof the functionality of a storage node 150 is shifted into a storageunit 152, transforming the storage unit 152 into a combination ofstorage unit 152 and storage node 150. Placing computing (relative tostorage data) into the storage unit 152 places this computing closer tothe data itself. The various system embodiments have a hierarchy ofstorage node layers with different capabilities. By contrast, in astorage array, a controller owns and knows everything about all of thedata that the controller manages in a shelf or storage devices. In astorage cluster 160, as described herein, multiple controllers inmultiple storage units 152 and/or storage nodes 150 cooperate in variousways (e.g., for erasure coding, data sharding, metadata communicationand redundancy, storage capacity expansion or contraction, datarecovery, and so on).

FIG. 10 is a flow diagram of a method for operating a storage cluster,which can be practiced on or by embodiments of the storage cluster,storage nodes and/or non-volatile solid state storages or storage unitsin accordance with some embodiments. In an action 1002, a first storageunit receives a direction regarding metadata or a portion of user data,from a storage node of a storage cluster. For example, the directioncould include a direction to store a portion of user data or a datashard, read a portion of user data or a data shard, construct data fromdata shards, read or write a parity shard, a direction to respond abouthealth, status or performance, etc.

In an action 1004, the first storage unit communicates directly with asecond storage unit via a pathway that does not require assistance fromany storage node or storage nodes. This communication could involvecommunicating about the metadata or the portion of user data. A suitableexample of communication about the metadata is communication of aheartbeat (which relates to the direction to respond about health,status or performance). Examples of communication about the portion ofthe user data would be to request a data shard from another storageunit, or to send a parity shard to another storage unit for writing intoflash memory of that storage unit. Further examples are readily devisedin keeping with the teachings herein. In an action 1006, the secondstorage unit receives the communication from the first storage unit, viathe pathway. More specifically, the second storage unit receives thecommunication directly from the first storage unit, not from a storagenode.

In an action 1008, the second storage unit determines an action, basedon the communication from the first storage unit. Depending on contentof the communication, the second storage unit could store data, storemetadata, read data or metadata and send it back to the first storageunit, respond to an inquiry from the first storage unit, and so on. Aresponse, where appropriate, could be sent from the second storage unitback to the first storage unit, or to another storage unit, via apathway that does not require assistance from any storage node orstorage nodes. Or, the action could be for the second storage unit tocommunicate with one of the storage nodes, or a compute node. Furtherexamples of actions are readily devised in keeping with the teachingsherein.

It should be appreciated that the methods described herein may beperformed with a digital processing system, such as a conventional,general-purpose computer system. Special purpose computers, which aredesigned or programmed to perform only one function may be used in thealternative. FIG. 11 is an illustration showing an exemplary computingdevice which may implement the embodiments described herein. Thecomputing device of FIG. 11 may be used to perform embodiments of thefunctionality for a storage node or a non-volatile solid state storageunit in accordance with some embodiments. The computing device includesa central processing unit (CPU) 1101, which is coupled through a bus1105 to a memory 1103, and mass storage device 1107. Mass storage device1107 represents a persistent data storage device such as a disc drive,which may be local or remote in some embodiments. The mass storagedevice 1107 could implement a backup storage, in some embodiments.Memory 1103 may include read only memory, random access memory, etc.Applications resident on the computing device may be stored on oraccessed via a computer readable medium such as memory 1103 or massstorage device 1107 in some embodiments. Applications may also be in theform of modulated electronic signals modulated accessed via a networkmodem or other network interface of the computing device. It should beappreciated that CPU 1101 may be embodied in a general-purposeprocessor, a special purpose processor, or a specially programmed logicdevice in some embodiments.

Display 1111 is in communication with CPU 1101, memory 1103, and massstorage device 1107, through bus 1105. Display 1111 is configured todisplay any visualization tools or reports associated with the systemdescribed herein. Input/output device 1109 is coupled to bus 505 inorder to communicate information in command selections to CPU 1101. Itshould be appreciated that data to and from external devices may becommunicated through the input/output device 1109. CPU 1101 can bedefined to execute the functionality described herein to enable thefunctionality described with reference to FIGS. 1-6. The code embodyingthis functionality may be stored within memory 1103 or mass storagedevice 1107 for execution by a processor such as CPU 1101 in someembodiments. The operating system on the computing device may beMS-WINDOWS™, UNIX™, LINUX™, iOS™, CentOS™, Android™, Redhat Linux™,z/OS™, or other known operating systems. It should be appreciated thatthe embodiments described herein may be integrated with virtualizedcomputing system also.

Detailed illustrative embodiments are disclosed herein. However,specific functional details disclosed herein are merely representativefor purposes of describing embodiments. Embodiments may, however, beembodied in many alternate forms and should not be construed as limitedto only the embodiments set forth herein.

It should be understood that although the terms first, second, etc. maybe used herein to describe various steps or calculations, these steps orcalculations should not be limited by these terms. These terms are onlyused to distinguish one step or calculation from another. For example, afirst calculation could be termed a second calculation, and, similarly,a second step could be termed a first step, without departing from thescope of this disclosure. As used herein, the term “and/or” and the “/”symbol includes any and all combinations of one or more of theassociated listed items.

As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”,“comprising”, “includes”, and/or “including”, when used herein, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. Therefore, the terminology usedherein is for the purpose of describing particular embodiments only andis not intended to be limiting.

It should also be noted that in some alternative implementations, thefunctions/acts noted may occur out of the order noted in the figures.For example, two figures shown in succession may in fact be executedsubstantially concurrently or may sometimes be executed in the reverseorder, depending upon the functionality/acts involved.

With the above embodiments in mind, it should be understood that theembodiments might employ various computer-implemented operationsinvolving data stored in computer systems. These operations are thoserequiring physical manipulation of physical quantities. Usually, thoughnot necessarily, these quantities take the form of electrical ormagnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated. Further, the manipulationsperformed are often referred to in terms, such as producing,identifying, determining, or comparing. Any of the operations describedherein that form part of the embodiments are useful machine operations.The embodiments also relate to a device or an apparatus for performingthese operations. The apparatus can be specially constructed for therequired purpose, or the apparatus can be a general-purpose computerselectively activated or configured by a computer program stored in thecomputer. In particular, various general-purpose machines can be usedwith computer programs written in accordance with the teachings herein,or it may be more convenient to construct a more specialized apparatusto perform the required operations.

A module, an application, a layer, an agent or other method-operableentity could be implemented as hardware, firmware, or a processorexecuting software, or combinations thereof. It should be appreciatedthat, where a software-based embodiment is disclosed herein, thesoftware can be embodied in a physical machine such as a controller. Forexample, a controller could include a first module and a second module.A controller could be configured to perform various actions, e.g., of amethod, an application, a layer or an agent.

The embodiments can also be embodied as computer readable code on anon-transitory computer readable medium. The computer readable medium isany data storage device that can store data, which can be thereafterread by a computer system. Examples of the computer readable mediuminclude hard drives, network attached storage (NAS), read-only memory,random-access memory, CD-ROMs, CD-Rs, CD-RWs, magnetic tapes, and otheroptical and non-optical data storage devices. The computer readablemedium can also be distributed over a network coupled computer system sothat the computer readable code is stored and executed in a distributedfashion. Embodiments described herein may be practiced with variouscomputer system configurations including hand-held devices, tablets,microprocessor systems, microprocessor-based or programmable consumerelectronics, minicomputers, mainframe computers and the like. Theembodiments can also be practiced in distributed computing environmentswhere tasks are performed by remote processing devices that are linkedthrough a wire-based or wireless network.

Although the method operations were described in a specific order, itshould be understood that other operations may be performed in betweendescribed operations, described operations may be adjusted so that theyoccur at slightly different times or the described operations may bedistributed in a system which allows the occurrence of the processingoperations at various intervals associated with the processing.

In various embodiments, one or more portions of the methods andmechanisms described herein may form part of a cloud-computingenvironment. In such embodiments, resources may be provided over theInternet as services according to one or more various models. Suchmodels may include Infrastructure as a Service (IaaS), Platform as aService (PaaS), and Software as a Service (SaaS). In IaaS, computerinfrastructure is delivered as a service. In such a case, the computingequipment is generally owned and operated by the service provider. Inthe PaaS model, software tools and underlying equipment used bydevelopers to develop software solutions may be provided as a serviceand hosted by the service provider. SaaS typically includes a serviceprovider licensing software as a service on demand. The service providermay host the software, or may deploy the software to a customer for agiven period of time. Numerous combinations of the above models arepossible and are contemplated.

Various units, circuits, or other components may be described or claimedas “configured to” perform a task or tasks. In such contexts, the phrase“configured to” is used to connote structure by indicating that theunits/circuits/components include structure (e.g., circuitry) thatperforms the task or tasks during operation. As such, theunit/circuit/component can be said to be configured to perform the taskeven when the specified unit/circuit/component is not currentlyoperational (e.g., is not on). The units/circuits/components used withthe “configured to” language include hardware—for example, circuits,memory storing program instructions executable to implement theoperation, etc. Reciting that a unit/circuit/component is “configuredto” perform one or more tasks is expressly intended not to invoke 35U.S.C. 112, sixth paragraph, for that unit/circuit/component.Additionally, “configured to” can include generic structure (e.g.,generic circuitry) that is manipulated by software and/or firmware(e.g., an FPGA or a general-purpose processor executing software) tooperate in manner that is capable of performing the task(s) at issue.“Configured to” may also include adapting a manufacturing process (e.g.,a semiconductor fabrication facility) to fabricate devices (e.g.,integrated circuits) that are adapted to implement or perform one ormore tasks.

The foregoing description, for the purpose of explanation, has beendescribed with reference to specific embodiments. However, theillustrative discussions above are not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Many modificationsand variations are possible in view of the above teachings. Theembodiments were chosen and described in order to best explain theprinciples of the embodiments and its practical applications, to therebyenable others skilled in the art to best utilize the embodiments andvarious modifications as may be suited to the particular usecontemplated. Accordingly, the present embodiments are to be consideredas illustrative and not restrictive, and the invention is not to belimited to the details given herein, but may be modified within thescope and equivalents of the appended claims.

What is claimed is:
 1. A storage system comprising: a plurality ofstorage nodes, each having a processor; a plurality of storage units,each having a controller and solid-state storage memory; a first pathwaythat couples the processors of the plurality of storage nodes and isconfigured to couple to a network external to the storage system; and asecond pathway that couples at least a first controller of a firststorage unit to a second controller of a second storage unit forcommunication, wherein the second pathway is a direct controller tocontroller coupling.
 2. The storage system of claim 1, furthercomprising: the first controller of the first storage unit configured tosend a write request and a data shard or a parity shard through thesecond pathway to the second controller of the second storage units; andthe second controller of the second storage unit configured to write thedata shard or the parity shard into the solid-state storage memory ofthe second storage unit, responsive to the write request.
 3. The storagesystem of claim 1, further comprising: the first controller of the firststorage unit configured to send an inquiry through the second pathway tothe second controller of the second storage unit; and the secondcontroller of the second storage unit configured to send a reply,through the second pathway to the first controller of the first storageunit, responsive to the inquiry, with the processors of the plurality ofstorage nodes being non-participatory in the communication.
 4. Thestorage system of claim 1, further comprising: the first controller ofthe first storage unit configured to send a read request for data ormetadata through the second pathway to the second controller of thesecond storage unit; and the second controller of the second storageunit configured to send the data or the metadata through the secondpathway to the first controller of the second storage unit, responsiveto the read request.
 5. The storage system of claim 1, furthercomprising: the first or second pathway coupling at least a firstprocessor of a first storage node to at least the first controller ofthe first storage unit; the first processor of the first storage nodeconfigured to send a direction to construct data from data shards,through the first or second pathway to the first controller of the firststorage unit; and the first controller of the first storage unitconfigured to send requests for the data shards through the secondpathway to further controllers of further storage units.
 6. The storagesystem of claim 1, further comprising: each of the plurality of storageunits configured to communicate a heartbeat through the second pathway.7. The storage system of claim 1, further comprising: the first pathwayincluding a network switch; and the second pathway including a PCI(peripheral component interconnect) Express bus.
 8. A storage systemcomprising: a plurality of storage nodes having a plurality ofprocessors; a plurality of storage units, each one of the plurality ofstorage units having a controller and solid-state storage memory; afirst pathway coupling the plurality of processors of the plurality ofstorage nodes to each other and configured to couple to a network; and asecond pathway coupling at least a first controller of a first one ofthe plurality of storage units and a second controller of a second oneof the plurality of storage units for communication withoutparticipation by the processors of the plurality of storage nodes. 9.The storage system of claim 8, further comprising: the first one of theplurality of storage units configured to have the first controllercommunicate a write request and a data shard or a parity shard to thesecond controller through the second pathway; and the second one of theplurality of storage units configured to have the second controllerstore the data shard or the parity shard in the solid-state storagememory of the second storage unit, responsive to the write request. 10.The storage system of claim 8, further comprising: the first one of theplurality of storage units configured to have the first controllercommunicate an inquiry to the second controller through the secondpathway; and the second one of the plurality of storage units configuredto have the second controller communicate a reply to the firstcontroller through the second pathway.
 11. The storage system of claim8, further comprising: the first one of the plurality of storage unitsconfigured to have the first controller communicate a read request fordata or metadata to the second controller through the second pathway;and the second one of the plurality of storage units configured to havethe second controller communicate the data or the metadata to the firstcontroller through the second pathway.
 12. The storage system of claim8, further comprising: one of the plurality of storage nodes configuredto have a processor communicate a direction to construct data from datashards to the first controller; and the first one of the plurality ofstorage units configured to have the first controller communicate atleast one request for at least one data shard to the second controllerthrough the second pathway.
 13. The storage system of claim 8, furthercomprising: the first and second ones of the plurality of storage unitsconfigured to have the first controller and the second controller eachcommunicate a heartbeat through the second pathway.
 14. The storagesystem of claim 8, further comprising: a network switch, through whichthe first pathway passes; and a PCI (peripheral component interconnect)Express bus, through which the second pathway passes.
 15. A method forcommunication in a storage system, performed by processors in thestorage system, comprising: communicating among two or more of aplurality of processors of a plurality of storage nodes of a storagesystem through a first pathway; and communicating among at least a firstcontroller of a first one of a plurality of storage units of the storagesystem and a second controller of a second one of the plurality ofstorage units through a second pathway, wherein each of the plurality ofstorage units has solid-state storage memory and wherein the secondpathway is a direct controller to controller coupling.
 16. The method ofclaim 15, further comprising: sending a write request and a data shardor a parity shard from the first controller of the first one of theplurality of storage units to the second controller of the second one ofthe plurality of storage units, through the second pathway; and writingthe data shard or the parity shard into the solid-state storage memoryof the second one of the plurality of storage units.
 17. The method ofclaim 15, further comprising: sending an inquiry from the firstcontroller of the first one of the plurality of storage units to thesecond controller of the second one of the plurality of storage units,through the second pathway; and sending a reply from the secondcontroller of the second one of the plurality of storage units to thefirst controller of the first one of the plurality of storage units,through the second pathway.
 18. The method of claim 15, furthercomprising: sending a read request for data or metadata from the firstcontroller of the first one of the plurality of storage units to thesecond controller of the second one of the plurality of storage units,through the second pathway; and sending the data or the metadata fromthe second controller of the second one of the plurality of storageunits to the first controller for of the first one of the plurality ofstorage units through the second pathway.
 19. The method of claim 15,further comprising: communicating a direction to construct data fromdata shards from a processor of one of the plurality of storage nodes tothe first controller of the first one of the plurality of storage units;and sending a plurality of requests for a plurality of data shards fromthe first controller of the first one of the plurality of storage unitsto further controllers of further ones of the plurality of storage unitsthrough the second pathway.
 20. The method of claim 15, furthercomprising: communicating a heartbeat from the first controller of thefirst one of the plurality of storage units to the second controller ofthe second one of the plurality of storage units through the secondpathway, and wherein the second pathway is a direct controller tocontroller connection.